Wired headphones to a cellphone, (like wired speakers to a stereo player) get the electric signal from the cable in an analog way, it contains both the energy and the signal.
That is enough to move the magnet&membranes in the speaker and reproduce the sound.
But for wireless speakers, the wireless signal does not transfert [enough] energy. And the headphone needs a source of electric power to : run the Bluetooth receiver/sender, and move the membrane to produce the sound.
actionyann t1_jdqzu01 wrote
Reply to Eli5: why do wired headphones that plug into your phone never need to be charged but wireless ones do? by exmxn
Wired headphones to a cellphone, (like wired speakers to a stereo player) get the electric signal from the cable in an analog way, it contains both the energy and the signal.
That is enough to move the magnet&membranes in the speaker and reproduce the sound.
But for wireless speakers, the wireless signal does not transfert [enough] energy. And the headphone needs a source of electric power to : run the Bluetooth receiver/sender, and move the membrane to produce the sound.
[Edited to add remark]